Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS5636260 A
Publication typeGrant
Application numberUS 08/411,538
Publication dateJun 3, 1997
Filing dateMar 28, 1995
Priority dateMar 29, 1994
Fee statusLapsed
Also published asDE69523803D1, EP0675624A1, EP0675624B1
Publication number08411538, 411538, US 5636260 A, US 5636260A, US-A-5636260, US5636260 A, US5636260A
InventorsGeoffrey Chopping
Original AssigneeGpt Limited
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Telecommunication customer interface
US 5636260 A
Abstract
A telecommunication network and switching system where digital circuits are supplied to customer terminals for dial-up services and where automatic testing of the access connections to the customer premises is performed while calls are not in progress. A loop test unit is provided at the customer's premises near to the customer digital line terminals able to detect a test sequence sent from an exchange when a call is not in progress, the test sequence being recognized by the loop test unit and a test sequence being returned to the exchange to enable the error performance of the link in both directions to be tested.
Images(3)
Previous page
Next page
Claims(5)
I claim:
1. In a dial-up telecommunications network of a type including an exchange; a plurality of customer line terminations; respective access links connecting each customer line termination to the exchange, and respective signaling links connecting the customer line termination to the exchange, said access links being operative to carry data, and said signaling links being physically separate from the access links and being operative to provide signaling between the customer line termination and the exchange;
an access link test apparatus for testing said access links, said access link test apparatus comprising:
a) means for determining when no call is in progress on an access link to be tested;
b) means being operative whenever no call is in progress for transmitting a known test sequence over the access link to be tested to the customer line termination;
c) a loop test unit connected to the access link to be tested, said loop test unit being located near to a customer's line termination, said loop test unit being operative upon detecting the known test sequence to generate a composite test sequence and transmit the composite test sequence over the access link to be tested to said exchange; and
d) means for analyzing the composite test sequence received at the exchange, thereby enabling both directions of the access link being tested to be checked.
2. The access link test apparatus as claimed in claim 1, wherein the access link to be tested has a primary rate of 2048 kbit/s.
3. The access link test apparatus as claimed in claim 1, wherein the means for determining when no call is in progress is operative to clear a switch path across a service switch of the exchange when it determines that no call is in progress, and is further operative for providing the known test sequence which is an idle pattern which is selected to be significantly different in format from a normal internal switch traffic format.
4. The access link test apparatus as claimed in claim 3, wherein the normal internal switch traffic format includes synchronous digital hierarchy (SDH) virtual containers.
5. The access link test apparatus as claimed in claim 4, wherein the known test sequence is based on a 2048 kbit/s frame format.
Description
BACKGROUND OF THE INVENTION Field of the Invention

Dial-up telecommunication services have been principally concerned with providing low bandwidth circuits between subscribers that are capable of carrying speech. Non dial-up telecommunications services have been provided as permanent private circuits at various bandwidths. Many of these private circuits consist of digital bit streams. Because the data carried by many of these digital private circuits is supplied by the customer, the operator of the telecommunication service does not have any control over the data transported and therefore may have no opportunity for routinely inserting known data formats in order to ensure that the bit streams are being correctly transported.

Although new multiplexing techniques often carry extra data in order to enable suitable performance measuring to be performed; these multiplexing techniques are often not suitable on certain parts of networks and in particular on the access interfaces to the subscriber's premises.

The introduction of digital dial-up services enables methods to be employed in telecommunication access networks to ensure the satisfactory performance monitoring of the digital circuits.

SUMMARY OF THE INVENTIONS

According to the present invention there is provided a telecommunications network and switching system offering dial-up switched services comprising:

an exchange including call control means and a service switch with exchange digital line terminations;

access links to customers for both digital circuits and signalling means;

a loop test unit at the customer's premises near to the customer digital line terminals;

and wherein means is provided to determine when no call is in progress on an transmission access link in order that the exchange digital line termination may transmit over that link a standard test sequence recognizable by the loop test unit so that a composite test sequence may be returned from the loop test unit to the same exchange digital line termination so as to enable the error performance of both directions of the link to be determined by that exchange digital line termination.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described by way of example by reference to the accompanying drawings in which:

FIG. 1 shows a diagrammatic representation of a transmission link and a signalling link from the exchange to the subscriber's digital line terminal.

FIG. 2 shows a diagrammatic representation of an exchange digital line termination with means for test pattern insertion and for test pattern monitoring.

FIG. 3 shows a diagrammatic representation of a test loop unit with means of providing a test loop and for test pattern monitoring.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

These figures and the following description are based on primary rate 2048 kbit/s transmission although the technique is applicable to other rates of transmission.

Referring now to FIG. 1 the transmission arrangements consist of a signalling link and a 2048 kbit/s link herein referred to as a 2 Mbit/s link. When the 2 Mbit/s link is carrying customer traffic it may be using one of many possible types of format. Unlike a permanent private circuit which can be carrying continuous customer traffic; a 2 Mbit/s dial-up service link is not always carrying customer traffic.

An ordinary subscriber low bandwidth analogue copper pair is in a reduced power state when not in use; a 2 Mbit/s line normally stays fully powered even when not carrying useful customer traffic. Consequently for a dial-up 2 Mbit/s service the link regularly has no call in progress.

For an ordinary analogue call if a subscriber believes that an established call has subsequently become disconnected or the quality of the connection is too bad then the subscriber can ring off in order to clear the call. Similarly if during a 2 Mbit/s call the subscriber equipment detects that the link is no longer operating satisfactorily the subscriber equipment may initiate the clear via the parallel signalling link. The means for operating a parallel signalling link is described in patent application no. GB 9319449.6 imported herein by reference. Whenever a clear is actioned the result is that there is no call in progress. Therefore there is an opportunity to test the 2 Mbit/s circuit from the exchange through to the subscriber's premises while there is no call in progress.

Once the call control function has determined that there is no call in progress the exchange digital line termination can be instructed to continuously insert a defined test sequence.

Referring now to FIG. 2 a means by which call control can indicate to the exchange digital line termination that there is no call in progress is by clearing a path across the digital switch providing that the resultant idle pattern from the switch can be clearly distinguished from normal data when a path is established. An example of such a case is when recognizable Synchronous Digital Hierarchy (SDH) formats are carried by the switch when a path is established and the idle patterns are chosen so that they cannot imitate the SDH formats.

A formatted test sequence based on a G.704 format of 32 time slots with a 4 bit cyclic redundancy (CRC-4) check comprises:

a time slot zero containing a frame alignment signal as well as a CRC-4 multiframe and correct CRC-4 check sums for the transmitted data;

a further 31 time slots containing standard and recognisable patterns.

Referring now to FIG. 3 a test loop unit functions as part of the access network and is not part of the subscriber's digital line terminal, though it is appropriate to site a test loop unit at the customer's premises. A test loop unit contains means for recognizing the test sequence that has been inserted by the exchange digital line termination. When the test loop unit has been continuously receiving the test sequence for longer than a defined period of time the test loop unit replaces the digital stream from the subscriber's digital line terminal with the test sequence from the exchange digital line termination except that the time slot zero contains a new frame alignment signal as well as a CRC-4 multiframe and correct CRC-4 check sums for the transmitted data. Also included in the time slot zero are any remote alarm indications signal and CRC-4 error indication bits relating to the 2 Mbit/s interface received by the test loop unit from the exchange digital line termination.

From the received time slot information including the remote alarm indication signal as well as the CRC-4 bits and the CRC-4 error bits, the exchange digital line termination can determine the error performance of both directions of transmission of the link from the exchange digital line termination as far as the loop test unit at the subscribers premises.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US4560842 *Apr 4, 1983Dec 24, 1985The General Electric Company, P.L.C.Telecommunication system loop-back unit
US4575584 *Jul 5, 1984Mar 11, 1986Honeywell Inc.Fail-safe digital phone
US4670898 *Jan 3, 1986Jun 2, 1987Harris CorporationDirect access test unit for central office
US4766594 *May 14, 1986Aug 23, 1988Fujitsu LimitedDigital network system having arrangement for testing digital subscriber line
US4984262 *Mar 2, 1990Jan 8, 1991Nippon Telegraph And Telephone CorporationTelephone network
US5224149 *Feb 26, 1992Jun 29, 1993Teltrend, Inc.Testing system for digital transmission lines
US5251204 *Sep 19, 1991Oct 5, 1993Fujitsu LimitedTransmission test system in a broadband ISDN
US5343461 *Aug 27, 1991Aug 30, 1994Ameritech Services, Inc.Full duplex digital transmission facility loop-back test, diagnostics and maintenance system
US5359646 *Apr 30, 1992Oct 25, 1994Bell Communications Research, Inc.Testing of distributed communications networks
US5361293 *Apr 16, 1992Nov 1, 1994Alcatel Network Systems, Inc.Line/drop testing from a craft terminal using test unit
US5490199 *Feb 21, 1992Feb 6, 1996At&T Corp.Non-intrusive network-based analysis of facsimile transmissions
AU1538376A * Title not available
DE3135561A1 *Sep 8, 1981Mar 17, 1983Siemens AgMethod for routine testing of digital telephone connections
EP0202648A2 *May 20, 1986Nov 26, 1986Fujitsu LimitedDigital network system having arrangement for testing digital subscriber line
EP0208327A1 *Jul 10, 1986Jan 14, 1987Siemens AktiengesellschaftDigital subscriber connection
EP0618714A1 *Mar 30, 1994Oct 5, 1994Telefonaktiebolaget Lm EricssonA device for testing subscriber lines in a digital switch
GB2141606A * Title not available
GB2158326A * Title not available
Non-Patent Citations
Reference
1"Ein neuer Standard verandert die Welt", Synhrone Digitale Hierarcie, pp. 56-59 and 62, Funkschau 14, 1991.
2 *Ein neuer Standard ver a ndert die Welt , Synhrone Digitale Hierarcie, pp. 56 59 and 62, Funkschau 14, 1991.
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US5835566 *Mar 29, 1996Nov 10, 1998Telecom Technologies, Inc.System and method for providing in-band and out-of-band testing of telecommunications network components
US5875230 *Dec 20, 1996Feb 23, 1999At&T Corp.Interactive measurement system and method for telecommunication networks
US5966427 *Sep 30, 1997Oct 12, 1999Siemens InformationApparatus and method for troubleshooting internet protocol telephony networks
US5974030 *Jun 14, 1995Oct 26, 1999Nokia Telecommunications OySubscriber multiplexer, a telephone system and a method for communicating the condition of a subcriber interface
US6181775May 10, 1999Jan 30, 2001Westell Technologies, Inc.Dual test mode network interface unit for remote testing of transmission line and customer equipment
US6278769Nov 3, 1999Aug 21, 2001Westell Technologies, Inc.Signaling method for invoking a test mode in a network interface unit
US6366644 *Sep 15, 1997Apr 2, 2002Cisco Technology, Inc.Loop integrity test device and method for digital subscriber line (XDSL) communication
US6453153 *May 11, 2000Sep 17, 2002At&T Corp.Employing customer premises equipment in communications network maintenance
US7706258 *Dec 22, 2004Apr 27, 2010Alcatel LucentSystem and method for detecting loops in a customer-provider bridge domain
CN100463419CDec 22, 2005Feb 18, 2009阿尔卡特公司System and method for detecting loops in a customer-provider bridge domain
WO2000069152A1 *Mar 9, 2000Nov 16, 2000Westell Technologies IncSignaling method for invoking a test mode in a network interface unit
Classifications
U.S. Classification379/22.01, 379/22.02, 379/29.01, 379/27.04
International ClassificationH04M3/30, H04M3/08, H04M3/22
Cooperative ClassificationH04M3/303
European ClassificationH04M3/30M2
Legal Events
DateCodeEventDescription
Aug 2, 2005FPExpired due to failure to pay maintenance fee
Effective date: 20050603
Jun 3, 2005LAPSLapse for failure to pay maintenance fees
Dec 22, 2004REMIMaintenance fee reminder mailed
Nov 27, 2000FPAYFee payment
Year of fee payment: 4
May 26, 1995ASAssignment
Owner name: GPT LIMITED, ENGLAND
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:CHOPPING, GEOFFREY;REEL/FRAME:007548/0424
Effective date: 19950505